function disableCtrlKeyCombination(e){
//list all CTRL + key combinations you want to disable
var forbiddenKeys = new Array("a", "s", "c", "u");
var key;
var isCtrl;
if(window.event){
key = window.event.keyCode; //IE
if(window.event.ctrlKey)
isCtrl = true;
else
isCtrl = false;
}else{
key = e.which;     //firefox
if(e.ctrlKey)
isCtrl = true;
else
isCtrl = false;
}
//if ctrl is pressed check if other key is in forbidenKeys array
if(isCtrl){
for (i = 0; i < forbiddenKeys.length; i++){
//case-insensitive comparation
if (forbiddenKeys[i].toLowerCase() == String.fromCharCode(key).toLowerCase()){
//alert("Key combination CTRL + "
//+ String.fromCharCode(key)
//+ " has been disabled.");                                   
return false;}
}
}
return true;}
